1. Field of the Invention
The present invention relates to radar detection device for performing radar detection in wireless communication in conformity with a predetermined standard.
2. Description of the Related Art
For use of a communication device that executes wireless LAN communication in conformity with IEEE 802.11, it is necessary to comply with a radio law established in a country in which the communication device is used. The radio law includes many provisions for a wireless LAN signal, and also includes a provision for a radar detection function. The provision for the radar detection function is one provision that coordinates between the wireless LAN signal and a radar signal to conduct communication while the wireless LAN signal and the radar signal do not interfere with each other in an environment in which the wireless LAN signal and the radar signal are used in the same wireless frequency band.
The radar detection function is essential for the communication device that is commercially introduced and uses a band of W53/56. A manufacturer of the communication device mounts the radar detection function on the communication device using a unique method (algorithm).
For example, Jpn. Pat. Appln. KOKAI Publication Nos. 2007-274659, 2006-86665, and 2007-49694 disclose techniques concerning the radar detection function.
In a device of Jpn. Pat. Appln. KOKAI Publication No. 2007-274659, the number of times exceeding a threshold and the number of times lower than the threshold are counted to make a determination of pulse effectiveness with a receiving-field-intensity-signal-level threshold detecting circuit and an up-down counter, and a determination of effectiveness of a stable pulse is made with a circuit that counts a time width from the beginning to the end of the effective pulse. The device of Jpn. Pat. Appln. KOKAI Publication No. 2007-274659 compares a receiving IQ signal of a constant time interval from the beginning of the effective pulse to signal power that is obtained by passband limitation with a steep digital filter.
A device of Jpn. Pat. Appln. KOKAI Publication No. 2006-86665 comprises a power computing section that computes received signal power in the wireless communication, a radar detecting section that compares the received signal power computed by the power computing section to a previously set radar threshold to detect a radar signal, and a radar detection determining section that informs an upper layer of a communication protocol of the radar detection when the number of radar signal detection times performed by the radar detecting section exceeds a previously set predetermined value within a constant time.
A network device of Jpn. Pat. Appln. KOKAI Publication No. 2007-49694 selectively measures N time intervals between adjacent and nonadjacent control signals, and selectively determines that an RF signal is a radar signal when the N time intervals are substantially equal to one another.
Many wireless LAN devices that are commercially introduced as a general-purpose product detects a signal as the radar pulse signal even if the signal has radar pulse received signal intensity lower than that required by the radio law.
There is no problem with the radar detection with a margin from the standpoint of the compliance with the radio law. However, convenience of an end user is hampered.
For example, it is assumed that a provision that “it is necessary to stop the use of wireless LAN communication for 30 minutes in the channel in which the radar is detected” is included in the radio law.
In such cases, when a level at which the signal is determined to be the radar pulse signal is set lower, possibly the radar detection is frequently generated to lengthen the wireless LAN communication stopping interval.
Accordingly, although Jpn. Pat. Appln. KOKAI Publication Nos. 2007-274659, 2006-86665, and 2007-49694 disclose the radar detection techniques, there is a need to further enhance accuracy and prevent expansion of a circuit scale.